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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
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<body>
    
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<script>
  // var a = 3
  // function fn(a) {
  //   a = a + 1
  // }
  // fn(3)
  // console.log(a);
  var obj = {
    name: 'bob',
    age: 13
  }
  var a = obj
  a.name = 'low'
  console.log(obj)
  // 匿名函数自调用(隐藏实现，不会污染外部命名空间
  // 如果没有通过对象来进行调用、this就是指向当前window
  (function() {
    var a = 3

  })()
</script>
</html>